Interpretive Summary: When corn is processed into ethanol, distilleries create a viscous syrup side product called condensed distillers solubles (CDS). CDS contains valuable nutrients, but it is difficult to dry. Currently, CDS is mixed with other ethanol side products, and then the whole mix is dried together. If the CDS could be dried on its own, this would create a high-value food or feed ingredient. In this experiment, we determined what drum drying conditions it takes to dry CDS and a physico-chemiclaly modified version of CDS (MCDS) into a shelf-stable form. We found that both CDS and MCDS could be dried using drum drying process conditions (time, temperature, and gap between the drums) that are feasible for industry. We found that MCDS required milder conditions than CDS in order to dry to the same level of stability. Thus, ethanol processors could drum dry CDS if they wanted, but they would save some time and energy if they chose to first modify the CDS (by removing some moisture-binding components) before drum drying it.

Technical Abstract:
Condensed distillers solubles (CDS) is a viscous, syrupy co-product of ethanol production from corn; CDS exhibits strong recalcitrance to drying due to its chemical composition, which includes a substantial amount of glycerol. The objectives of this study were to determine the drum drying performance of CDS under various processing conditions and compare CDS’s drum drying performance to that of glycerol-reduced, physico-chemically modified CDS (MCDS). Material type (CDS versus MCDS), dwell time, drum internal steam temperature, and gap width were evaluated for their effects on the final moisture content, water activity, and color of the dried product. While both CDS and MCDS could be dried to a range of endpoint moisture contents, dried CDS exhibited a narrow range of water activity compared to that of MCDS. Gap width was found to be the predominant factor affecting dried product color. This work demonstrates that CDS can be drum-dried to a dark orange, dough-like consistency with a minimum water activity of 0.45. In addition, MCDS can be readily drum-dried into a shelf-stable, flaked product with a pleasing appearance.